1) People in sunny climates evolved darker skin. When they migrated to places like Scandinavia, their ancestors evolved light skin. Now people live all over a

1) People in sunny climates evolved darker skin. When they migrated to places like Scandinavia, their ancestors evolved light skin. Now people live all over and migrate readily, and don't want to wait for their ancestors to evolve skin to match the climate. 2) Prehistoric people had low life expectancies, so if they died of melanoma at age 45, it wasn't a big deal, or they never got to die of melanoma because they were killed by a wild animal or an infection before then. Now people expect to live to an old age, don't have problems with wild animals or wars with neighboring tribes (at least in developed nations), they have antibiotics and neosporin and band-aids to avoid infection from minor wounds, and don't want to die of melanoma.